Production of aluminum alloy castings, for example massive production of certain automobile engine parts, (such as cylinder heads), is usually made in permanent or semi-permanent type molds, in contrast with expendable molds made of sand which are used for only one casting. The semi-permanent molds are provided with means for heating, cooling, automatic opening and closing, etc. to complete a full casting cycle. Usually one operator serves several molds, and some operations such as core setting, mold filling, and extraction of the casting are made with the help of robot arms, programmed for performing these repetitive operations with accuracy in time and space.
The production cycle of the casting process comprises the following operations, directly related to the mold: (A) mold cleaning; (B) core setting; (C) mold filling and cooling; and (D)extraction of casting, followed by breaking and elimination of external sand cores and removal of runners. The casting is then heat-treated, if necessary, finished and inspected. The production process currently in operation involves the use of fixed semi-permanent molds. One such process requires at least one operator and three robots per mold. An alternative process uses a revolving platform, typically with 4 to 6 molds mounted thereon, which are served by two or three operators and three robots for said five molds. The productivity of the revolving platforms has been relatively satisfactory but can be improved according to the present invention. The revolving platform also has some drawbacks, for example the mass of the revolving platform is on the order of 50 metric tons, which requires high capacity motors and equipment to rotate it from one station to the next. Also, if one of the molds breaks down and has to be repaired, most of the time, the whole platform has to be shut down with the consequent loss of production of the other molds thereon.
The present invention overcomes the disadvantages of the presently utilized revolving platforms and allows for higher productivity of the casting process.
This invention thus results in multimillion dollar savings in capital investment and upkeep costs of the revolving platforms and the maintenance costs of such equipment. The casting plants are therefore greatly simplified.
There have been some proposals in the past addressed to upgrade the efficiency of foundries, where molds undergo a sequence of operations. All of prior art shows circular paths along which the molds circulate and are positioned at several stations for performing the required operations. Examples of the prior art are found in U.S. Pat. No. 3,627,028 to Carignan, U.S. Pat. No. 4,747,444 to Wasem et al, U.S. Pat. No. 4,299,629 to Friesen el al., U.S. Pat. No. 4,422,495 to Van Nette, U.S. Pat. No. 3,530,571 to Perry, U.S. Pat. No. 5,056,584 to Seaton and U.S. Pat. No. 3,977,461 to Pol et al. None of these patents however teach or suggest the arrangement proposed by the Applicants and its advantages in productivity. Some of these patents teach for example to synchronize the movement of the molds with the movement of ladles containing the liquid metal, but none suggest to have linear paths for the molds along which the molds can travel and meet the servicing robots for pouring the molten aluminum and extracting the casting one at a time and each one under wholly independent operation of the others. The prior art does not suggest to include one station where each mold can be positioned for maintenance, which is practical in the linear path arrangement and not in circular paths, where the molds can be positioned when needed without interfering in any way with the casting cycle of the other molds.